The invention relates to a drive train assembly for a motor vehicle and to a method for controlling it.
From the prior art, drive train assemblies are known in which in succession an internal combustion engine, a starter clutch, an electrical machine, a drive clutch, and an automatic transmission, preferably an automated manual transmission, are disposed. The electrical machine can be used, among other purposes, as a starter-generator. Typically, the components listed are adapted to the various situations that occur during operation of the motor vehicle in a coordinated way in terms of their operating states. Usually, such control is effected via a central engine control unit, which specifies set-point variables to final control elements assigned to the various components of the drive train assembly. For instance, the starter clutch and the drive clutch have separate clutch positioners, with which a status (open or closed) of the clutches can be set selectively. Reducing the number of parts in the components present in the drive train assembly is a goal for manifold reasons. On the one hand, fewer parts means reduced material costs and reduced effort and expense for assembly, so that production costs can be reduced. On the other hand, the attendant space saving makes it possible to optimize the installation space, and the reduced weight then reduces fuel consumption on the part of the motor vehicle.
An additional reduction in the number of parts is possible as a result of the drive train assembly according to the invention and the method for controlling its operation. Because a common double clutch positioner is assigned to the two clutches, which enables a selective setting of the applicable status (open or closed) of the clutches by assumption of a corresponding switching position, one of the two usual clutch positioners can be dispensed with.
In a preferred embodiment of the invention, a control unit for specifying the switching positions is assigned to the double clutch positioner. The specification of the switching positions is effected as a function of the operating states and/or operating parameters of the assemblies present in the motor vehicle. In many operating situations, recourse can be had to time-tested control mechanisms.
The double clutch positioner preferably has up to four switching positions, whose location can be defined by the specification of different disengagement paths for the double clutch positioner, in which
both clutches are closed (coupling status Z1), or
the starter clutch is open and the drive clutch is closed (coupling status Z2), or
both clutches are open (coupling status Z3), or
the starter clutch is closed and the drive clutch is open (coupling status Z4).
In a further preferred embodiment of the invention, only three switching positions in the double clutch positioner are implemented, and either the aforementioned clutch status Z3 or the clutch status Z4 is dispensed with. In operating situations of the motor vehicle in which the aforementioned clutch statuses would be necessary, this is compensated for by a control of the operating states of the assemblies present in the motor vehicle. To that end, it is for instance possible, via the control unit, to actuate means with which the manual transmission can be shifted into a neutral position.
The present invention furthermore discloses especially preferred embodiments for the case where the clutch status Z4 is dispensed with. In at least the following operating situations,
starting of the engine;
the shifting operation in the transmission;
a static mode of the engine; and
hard braking, for example ABS braking, with drive effected via the engine,
the missing clutch status Z4 is compensated for in that the clutch status Z1 and a neutral position of the transmission are set. To change gears, the transmission must be shifted without load and synchronized by means of controlling the engine and the electrical machine. It is also preferred that with the clutch status Z4 dispensed with, the startup of the motor vehicle be designed such that the clutch status Z1 and a gear are selected in the transmission, and the drive takes place via a sliding starter clutch.
In a further preferred embodiment of the invention, in which the clutch status Z3 has been dispensed with, a pulsed start of the engine can be realized by providing that at least intermittently, the clutch status Z2 and the neutral position of the transmission are specified to the double clutch positioner. If the clutch status Z3 is dispensed with, hard braking, such as ABS braking, with drive via the electrical machine, can be designed such that shifting is done first into the clutch status Z1 and then into the clutch status Z4. The closure of the clutch K2 can be delayed via additional elements, until the status Z1 is attained.